Abstract

In this chapter, we will characterize the communication performance over multi-user MIMO channels, also known as point-to-multipoint and multipoint-to-point MIMO channels. We begin by explaining why the capacity gains achieved by point-to-point MIMO are limited in many practical scenarios, as a motivation for identifying an alternative way to use multiple antennas. The focus will then be on serving multiple users connecting to the same wireless system, which raises the question of whether the users should be assigned orthogonal or non-orthogonal transmission resources. To answer this, we will extend the capacity concept to the multi-user setting and discover how the use of multiple antennas radically changes the situation. We will adapt the precoding, combining, and power allocation schemes from previous chapters to maximize performance in the multi-user context. The tradeoff between non-linear and linear signal processing methods will finally be explored.